DE1804410A1 - Electrical signal transmission system - Google Patents

Description

Western Electric Company Incorporated W.B. Gaunt Jr. 17

New York, N.Y. 10007 U.S.A.

Electrical signal transmission system

The invention relates to an electrical signal transmission system with a bidirectional network that is connected to the transmission channel that transmits the signals in both directions. It relates in particular to a bilateral message or similar transmission system that is used for transmission The use of hybrid circuits is dispensed with in both directions.

In the case of telephone or other communication systems, the signals are exchanged between the stations! with the help of transmission lines, which are connected to one another via a switching network. It is often desirable to have one or more bilateral transmission circuits to switch on the connection path between the stations. Such transmission circuits can help the signal losses and reflections by improving the impedance matching between the connected stations and to decrease the network.

Known bilateral transmission circuits use a pair

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of facility amplifiers (these are amplifiers, the signals only in one direction; generally only in the direction of its entrance amplify to their output), which are inserted into the circuit in such a way that that they allow the circuit to operate on both sides, i.e. in both directions. Circuits of this type where the output of one amplifier is connected to the input of the other amplifier, very often use hybrid circuits between the stations and the transmission line ^ so that the signals cannot get back to the signal source from the connected stations and thus do not generate any feedback distortion.

The transmission circuits mentioned above require a special specially balanced circuit, often with special Transformers, the so-called fork transformers, are equipped, which are relatively expensive. These known circuits They also have the disadvantage that they are optimal Signal transmission an adaptation network for adapting the fork transmitter need to the message line.

The object of the invention is to avoid these disadvantages.

The invention solves this problem in that in an electrical Signal transmission system with a bidirectional network which is connected to the transmission channel that carries the signals

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in both. This bidirectional network transmits directions first and second receiving circuit for signals from a first and second direction, respectively. It also contains a logic circuit between the receiving circuits to link their signals and to generate a link signal. This bidirectional network also contains a first control circuit between the logic circuit and the first receiver maintenance is arranged and the link signal for first receiving circuit transmits. There is also a second ■

Control circuit provided between the logic circuit and the second receiving circuit is arranged and transmits the logic signal to the second receiving circuit. Transferred here the first and second receiving circuit, depending on the logic signal, the signals in the first and second, respectively Direction of the transmission channel in the desired direction, the receiving circuits with respect to the signals in the first and second direction are in antiphase. i

Further features of the invention can be found in the subclaims.

Since the signal transmission system of the invention without the use of hybrid circuits with relatively complex fork transmitters and

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Adjusting circuits gets by, it has the advantage of being larger Economy compared to the previously known two-sided signal transmission circuits.

In the following the invention is explained with reference to drawings Embodiments described in more detail; Show it:

1 shows a general block diagram of the invention,

2 shows a schematic representation of an exemplary embodiment the invention,

Fig. 3 is a schematic representation of another embodiment of the invention and

FIGS. 4A and 4B show two different damping networks which are used in the arrangements according to FIG and 3 can be used.

Short description:

The signal transmission system of the invention consists of a bidirectional transmission circuit (two-way transmission) that is switched on between a station and a transmission network and which avoids the use of hybrid circuits. The two-sided Transmission circuit transmits the outgoing signals from the station to the transmission network and the incoming signals

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from the transmission network to the station. It contains a feedback network which transmits a signal responsive to the sum of the outgoing and incoming signals both to the connection point of the station with the bilateral transmission circuit and to the connection point of the transmission network with the bilateral transmission circuit. That part of the sum signal which corresponds to the outgoing signal is out of phase with this output signal at the point of contact of the station \

fed back to the bilateral transmission circuit, so that the outgoing signal is partially suppressed. In this way, stable transmission without hybrid switching is achieved. The signals are exchanged simultaneously between the network and the station via this bifurcated two-way transmission circuit.

In the bilateral transmission circuit, the incoming

Incoming and outgoing signals to a summing amplifier over- ^

carry, whose output signal is the sum of the outgoing and incoming Signals is proportional. The output signal from the summing amplifier is sent to the connection point via a coupling device transmitted back between the bilateral transmission circuit and the station and via a further coupling device also to the connection point between the transmission network and the

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retransmit bilateral transmission circuit. At the junction the bilateral transmission circuit with the station that part of the output signal of the summing amplifier which corresponds to the outgoing signal suppresses the outgoing signal. That part of the output signal of the summing amplifier however, which corresponds to the incoming signal is transmitted to the station.

The outgoing and incoming signals are each via first and transmit second attenuation networks to the summing amplifier. Also the coupling elements between the summing amplifier, the transmission network and the first station contain damping networks. These damping networks are corresponding to the impedances the station and the transmission network are matched so that the ratio of the outgoing signals to the transmission network occur to the outgoing signals from the station equal to the ratio of the damping factor of the first damping network to the damping factor of the second damping network. This ratio is also equal to that of the network incoming signals to the incoming signals that were transmitted to the station. This comparison of the damping networks simultaneously allows a suitable impedance matching between the bilateral transmission circuit and the station and between the

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bilateral transmission circuit and the transmission network.

Furthermore, the damping network between the station and the summing amplifier and the damping network which couples the summing amplifier to the transmission network is a non-linear, dynamically pressing network, the non-linear voltage functions of the networks being proportional to one another. The dynamically pressing damping network, together with the \

Summing amplifier and the feedback connection that the outgoing Signal that passes through this press is dynamically pressed, while the incoming signal, which passes through the non-linear coupling circuit of the bilateral transmission circuit, is dynamically stretched. The compander operation is realized while at the same time the transmission ratios and the impedance matching mentioned before are maintained.

Detailed description:

Fig. 1 shows a signal transmission system according to the invention, in which the bilateral transmission circuit 1 between the communication line 10 and a common transmission network 2 and the bilateral communication circuit 3 between a communication line 14 and this network 2 is switched on. The network-

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Werk 2 can, for example, be a switching network that contains switching devices. Other bilateral transmission circuits, which are not shown, can also be connected to the transmission network 2 via further lines, such as 33, 34, for example and 35, be connected. The transmission lines, for example 10, can also be with a single station 4 or with a whole Series of stations, as indicated in Fig. 1, via a suitable switching network, for example a time division multiplex system, connected s a.

To clarify the expression "outgoing signal" is intended below a signal can be understood which is transmitted from the station 4 to the bilateral transmission network 2 and for the common Network 2 is determined. Accordingly, the term "incoming signal" is understood to mean a signal which is from the common transmission network 2 is transmitted to the bilateral transmission network and is intended for the station 4.

An outgoing signal from station 4 is transmitted via line 10 to the Station coupler 20 transmitted, which transmits this signal via line 21 to the summing amplifier 22. One from the transmission network 2 incoming signal is transmitted over line 32 to transmission line coupler 24. This incoming

9098207 112a

Signal can for example from the bilateral transmission circuit 3 or other bilateral transmission circuits not shown come. This signal is transmitted via line 23 to the summing amplifier 22. The output signal of the Summing amplifier 22 is proportional to the sum of the outgoing Signal on line 21 and the incoming signal on line 23. This output signal from the summing amplifier 22 is below referred to as the sum signal. This sum signal is sent via line 27 to the station coupler 20 and via line 29 transmitted back to the transmission network coupler 24.

The sum signal transmitted back to the station coupler 20 contains a part which corresponds to the outgoing signal and a part which corresponds to the signal arriving from the transmission network 2. That component of the sum signal at the station coupler 20 that corresponds to the outgoing signal is partially derived from the outgoing signal Signal on line 10 suppressed, resulting in stable behavior the signal transmission stops. However, that component of the sum signal which corresponds to the incoming signal and which occurs on line 27 is transmitted to station 4 via line 10. Similarly, the signal component of the The sum signal, which represents the incoming signal, is transmitted via the line 29 to the transmission network coupler 24. she

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is partially suppressed by the incoming signal via line 32. The outgoing signal on the line 29 is transmitted to the transmission network 2 via the line 32. The outgoing signal is from there to other bilateral transmission circuits, for example via line 40 to the bilateral transmission circuit 3, transferred. The negative feedback, which is a partial suppression of the outgoing signal in those bilateral transmission circuits that are connected to the connected stations, allows the simultaneous transmission of signals between the stations without the use of hybrid circuits.

The couplers 20 and 24 contain attenuation networks that are so aligned are that they are the impedance of the bilateral transmission circuit 1 at the connection point with line 10 to match the characteristic impedance of line 10. The same goes for that too Impedance matching of the bilateral transmission circuit 1 and the connection point with the line 32.

A transmission method is used in carrier frequency systems, which is called the Presser-Dehner concept and serves to improve the signal-to-noise ratio. The presser rearranges the various amplitudes of an analog signal into predefined levels before transmission. This means that the

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different in the amplitude levels of the signals are reduced. on in this way the amplitude range is limited.

The expansion of the signals is complementary to the compression and causes it the restoration of the original amplitude relationships of the analog and previously pressed signal. In this way, the difference in the amplitude levels of the signals is increased again.

Therefore the attenuation networks in connection with the sum λ

mier ver more 22 are dimensioned so that they pass through squeeze outgoing signals in their dynamics and stretch the dynamics of the incoming signals again, while simultaneously Impedance matching between the transmission circuit and the lines 10 and 32 maintained.

2 shows an exemplary embodiment of the two-sided transmission circuit 1, in which a pnp transistor 114 and the damping networks 119 and 125, the station coupler 20 and an npn tran- f sistor 130 and the attenuation networks 127 and 129 the transmission network coupler 24 form. The summing ver more 22 is shown with the internal resistance 122 in this embodiment.

The circuit of Fig. 2 operates as follows: An outgoing

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The signal is transmitted from the station 4 to the line 10, which may have _{the characteristic impedance Z 1.} This signal causes a current I ₁ which flows into the emitter 115 of the pnp transistor 114. A voltage arises at the emitter 115 which is _{equal to the voltage drop I 1} Z _{1 of} the outgoing signal. The current L is transmitted via the emitter-collector path of the transistor 114 to the line 118 with almost no voltage drop. The current is routed from this line to the damping network 119. The transistor 119 can be made up of linear elements, as shown in FIG. 4A, or else contain non-linear elements such as the anti-parallel diodes 314 and 315 shown in FIG contains elements and has a damping factor of m ^. Hence, a current i. at the entrance of the

H
fungsnetzwerks 119 a current mr at the output of this network

result. This current also flows through resistor 121 im Summing amplifier 22.

If there is no input from line 32, then will the signal voltage across resistor 121 in amplifier 22 is as follows amplifies that a signal voltage is produced at the output of the amplifier as a function of the current jjj-. This signal voltage passes through the damping network 125 and is attached to the base 116

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of transistor 114 is applied. This voltage is also present via the damping network 127 at the base 131 of the npn transistor 130. It is assumed that the damping networks 125 and 127 have linear elements and the damping factors η and n ₆ , respectively. Because of the negative feedback connections in the bilateral transmission circuit, a stable signal voltage is achieved because the signal voltage at the base 116 outgoing from the damping network 125 is in phase opposition to the signal voltage of the outgoing signal at the emitter 115

Base 131 is applied, this outgoing signal voltage is over the base-emitter junction of transistor 130 coupled; she appears at emitter 133 and is applied to line 32.

It is also assumed that the line 32 has a characteristic impedance Z ₀ . A current i _o therefore flows out of the emitter 133 and causes an essentially equal current flow in the collector 132. The current i ″ runs through the damping network 129 and is also conducted through the resistor 121. This stream will *

by the factor m »damped, since this is the damping factor des Attenuation network 129 is. Hence, flow through the resistance

¹ I * 2

a total stream of —-— - ——. - · -..- ... ..-

Hi ₁ m ₂

The current i, which flows through the wave resistance, causes

90-9820 / 1 1 2 δ

a signal voltage ν «, which is applied to the emitter 133. This signal voltage is essentially the same as the signal cooling on the base 131. Therefore the signal voltage at the output of the amplifier is 22 n-Vg. / If the gain of the amplifier is 22 A,

ⁿ 2 ^V 2 must at the input of the amplifier 22 a signal voltage of

lie. The signal voltage at the input of the amplifier 22 is, however, the voltage across the resistor 122 as a result of the currents - ■■ - and. The following relationship is obtained

^ 2

i i η ν

where R is the value of resistor 121. This relationship arises because the currents I ₁ and i _{o flow} in opposite directions. The transistors 114 and 130 are of the opposite conductivity type, so that the coupling of the collector currents between the two transistors can be realized.

In order to show that the impedance of the bilateral transmission circuit on line 10 is equal to the characteristic impedance of this line, the signal voltage becomes. V ₁ at emitter 115, which turns out to be. Consequence of the streamS ^ i ₁ . adjusts in line 10, calculated. The input impedance Z. *., T "., Can then be evaluated. .This voltage V ₁ is the same as the voltage at the output ₍ des

9 0 9 8 2 0/11 2 öc M \ ■ < ^ i

ORIGiMAL INSPECTED

/ 5 "

Amplifier 22 ( _no v _o ), which is divided by the damping factor _{n i}

Ct at X

must be dated, since the signal voltage n_v _{2 is influenced} by the damping network 125. By linking equation (1) with the last-mentioned expression, the input impedance of the two-sided transmission circuit is calculated

m well ,. ⁿ i ^m i

^m 2 ⁿ 2 ^Z 2 ⁺ " ¹ ^

If the gain A of the amplifier 22 is very large, so that

ⁿ l ^m l
the term - can be neglected, then ä is simplified

^m 2 ⁿ 2 ^Z 2 "

equation (2) to -. By selecting the damping factors such that

^m 2 ⁿ 2 ^Z l

^m l ⁿ l ^Z 2

then the input impedance Z. can be made equal to the characteristic impedance Z _{1 of} the line 10.

It was previously assumed that the damping network works

bilateral transmission circuit containing linear elements such as "

they are indicated in Figure 4A. When a damping network is used as the damping networks 119 and 127 as described in Pig. 4B is shown, the diodes 314 and 315 have the effect that signals with a higher voltage are attenuated more than those with a smaller 'j

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Tension. This limits the signal voltage across the "diodes, so that the dynamics of the output signals of the network are compressed. Such nonlinear elements can be used in the circuit without changing the impedance matching explained above, provided that the nonlinear damping factor Hi ₁ in the mold with the non-linear damping factor n _o compliance

1 a

ⁿ 2 is true. In this case the ratio of attenuation becomes the

^m l equation (3) not further influenced by the nonlinearities.

The bilateral transmission circuit works in the exemplary embodiment of the invention as a compandor, whose output signals are pressed in terms of their dynamics and whose input signals are stretched if the nonlinear damping network according to Fig. 4B, which was previously explained is used. To prove this, the transfer function of the bilateral transfer circuit calculated. Provided that the wave resistance of the line 10 at its point of contact with the bilateral Transmission circuit is adapted, equation (1) can be as follows be given:

^V l : ■ I2_ Y2. ■ ...

^m 1 ^Z 1 " ^m 2 ^Z 2" AR '. ^{l J}

By transforming equation (4), the transfer function is obtained:

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^V 2 • ^m l ^Z 1 1 m ^ Z 1 ^V l m Z 2 AR

804410

(5)

If the gain A of amplifier 22 is sufficiently high,

^m l ⁿ 2 ^Z l
then the expression τ · = - is negligible, so that

^m 2 ^Z 2
the transfer function simplified to = -. The transmission

^m l ^Z l

supply function, which the signal voltage on the line 10 as a function of the signal voltage, which describes via the line 32 to the two-sided transmission circuit, is inversely pro fj

proportional to the previously specified relationship. The reason for that is the symmetry of the bilateral transmission circuit. if

^m 2
therefore the ratio is less than one, so that a grain

pression of the outgoing signals is effected, then the incoming ones Signals stretched. The reason for the desired compression and elongation is the non-linear damping factor m ...

Fig. 3 shows the two-sided transmission circuit 1 according to the another embodiment of the invention. In Fig. 3, the station coupler 20 has the npn transistors 214 and 233 and the attenuation networks 219 and 229. While npn transistors are used in this circuit arrangement, it is conceivable that pnp transistors or similar coupling links can be used.

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The transmission network coupler 24 contains the PNP transistors 224 and 240 and the damping networks 220 and 231. The positive DC voltage source 250 supplies the transistors 214 and 224 with positive DC voltage, while the negative voltage source 252 supplies the transistors 233 and 240 with a negative counter voltage. The inputs of the amplifiers 22 are connected to the attenuation networks 219 and 220 and its output are connected to the inputs of the damping networks 229 and 231. The amplifier 22 generates a signal which is proportional to the sum of the output signals of the attenuation networks 219 and 220. For the description it is assumed that the damping networks 219 and 220 have the damping factors m. and in «, respectively. The damping factors

1 a

of the attenuation networks 229 and 231 are n ₁ and η, respectively. It is further assumed that an outgoing signal voltage is applied to line 10 while no signal is applied to line 32.

The signal voltage which is applied to the line 10 generates a signal voltage V ₁ at the base 216 of the transistor 214. This voltage V ₁ is also applied to the emitter 215 without any significant voltage drop] it is therefore also applied to the damping network 219. The off input voltage of the damping network 219 betrSigt- ^ sv

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^V l

thus - - because this has the damping factor m. This signal voltage is applied to one input of amplifier 22. The output signal of the amplifier 22 is via the damping network 229 and the base-collector path of the transistor 233 are fed back to the line 10 and the base 216 of the transistor 214. The output signal of the amplifier 22 is also via the damping network 231 and the base-collector path of the transistor 240 to line 32 and base 226 of the transistor 224 given.

Depending on the signal voltage V ₁ , a current i "flows into the line 32 and generates the voltage v" at the output impedance of the line 32 and the connected transmission network. This output impedance is denoted by Z_. The voltage v ₂ is in turn transmitted to the second input of the amplifier 22 via the transistor 224 and the damping network 220, so that the voltage is present at this input. Under the fore

The suspension that resistor 245 has the value R occurs on |

^Rv 2
Emitter 243 the voltage - = -. This voltage requires

^ ⁿ 2 ^Rv 2

2 output of the amplifier in the feedback branch a voltage ---

^Z 2

This voltage divided by the amplification factor A of the amplifier 22 is

n "Rv _r AZ ₂

(6)

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It is at the summing point in amplifier 22. The voltages at the base 235 and consequently also at the emitter 236 are essentially

ⁿ 2 ^Rv 2
borrowed - , where R is the value of resistor 238.

ⁿ l ^Z 2
The current flow from emitter 236 is essentially the same as the current flow in collector 234. The current flowing into base 216 is negligible because of the high gain of this transistor and because the load current on line 10 is the current flowing in collector 234. Therefore

The input impedance of the circuit according to FIG. 3 at the connection of the line 10 can be calculated as a function of the current i flowing into the collector 234 and as a function of the voltage applied to the base 216 via the line 10. The calculation is based on the fact that the line 10 and the connected station have a common output impedance of Z ₁ . Combining equations (6) and (7) results in the following input impedance Z.:

V ₁ m ₁ n _l mn., R

X ₁ m ₂ n ₂ 2 A "

If the amplification factor A is large enough to reduce the second

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Make the term of equation (8) negligible, then the input impedance is

■ n _± m-

^z - 'M ^z > ■ ^t9>

As has already been explained in connection with FIG. 2, the input impedance Z. can be made equal to the impedance Z-, provided that the conditions of equation (3) are met.

As already explained in connection with FIG. 2, ^

damping networks 219 and 231 include nonlinear components such as diodes 314 and 315 shown in Figure 4B. As long as the damping factors m. And n ~ are identical have non-linear characteristics, the input impedance remains at the connection point of the line 10 with the transmission circuit according to FIG. 3 is adapted to the characteristic impedance of the line 10. Because the symmetry of the circuit according to FIG. 3 is also the input impedance at the connection point of the line 32 with the two-sided transmission circuit adapted to the wave resistance of the line 32. Therefore, according to the invention, permits the bilateral transmission circuit according to Fig. 3 an impedance matching with the common transmission network, which is connected to line 32 and with station 4 or with the direction of the group of stations, which is connected to line 10.

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The transfer function of the two-sided transfer circuit according to FIG. 3 can, taking into account the adaptation conditions, previously explained can also be calculated. When the impedances of lines 10 and 32 to the bilateral transmission circuit are adjusted, the transfer function can be calculated by transforming equation (6). she is

V ₁ m ^ r " ⁰ ^

m ₂ ..AZ ₂ .

^m 2 As before, the transfer function - if the amplifier

^The factor A is sufficiently high. Because of the symmetry of the

tion, the transfer function is in the opposite direction.

Therefore, if all damping networks contain linear components

^m 2 "

and the ratio is less than one, the outgoing becomes

Signal from line 10 attenuated and the incoming signal from line 32 reinforced. When nonlinear components in the attenuation networks 219 and 231, as in Pig. 4B is used the dynamics of the outgoing signal are compressed and those of the incoming signal are stretched. The reason for this is that nonlinear damping factor m ... This causes large Voltages are attenuated more strongly than small voltages, whereby the output signal voltages of the damping network are limited will.

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"180-410

The exemplary embodiments of the invention described above are intended to explain the principle of the invention. So is it is also conceivable to specify other arrangements which, for example, use only npn transistors or only pnp transistors. Even the station coupler 20 and the transmission network coupler 24 in FIG. 1 may contain transformers which provide the coupling both the signals applied to the bilateral transmission circuit and the feedback signals transmitted in the bilateral Transmission circuit are generated, make.

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Claims (4)

. Patent pending 1.Electrical signal transmission system with a bidirectional network, which is switched on in the transmission channel that transmits the signals in both directions, characterized in that, that the bidirectional network (1) Fig. 1 has a first (20) and second (24) receiving circuit for signals from a first and second direction, also a logic circuit (22) between the receiving circuits for linking their signals and Generation of a logic signal, furthermore a first control circuit (27) between the logic circuit and the first Receiving circuit is arranged and which transmits the link signal to the first receiving circuit and finally a second Control circuit (29) which is arranged between the logic circuit and the second receiving circuit and the logic signal transmits to the second receiving circuit, and that the first and second receiving circuit depending on the Linking signal the signals in the second and first direction on the transmission channel in the desired direction and that the receiving circuits are in antiphase with respect to the signals in the first and second directions. 2. Electrical signal transmission system according to claim 1, 909820/1128 characterized in that the first receiving circuit (20; Fig. Ij 2) a first damping network (119; Fig. 2), the second receiving circuit (24) a second damping network (129), the first control circuit (27) a third damping network (125) and the second Control circuit (29) have a fourth damping network (127). 3. Electrical signal transmission system according to claim 2, the communication channel of which has different wave resistances at its connection points with the bidirectional network, characterized in that the first receiving circuit (2Oj ¹ Fig. 1) % the adjustment of the characteristic impedance at the first connection point (10-1) and the second receiving circuit (24) adjusts the characteristic impedance at the second connection point (32-1). 4. Electrical signal transmission system according to claim 2, characterized in that the first (119; Fig. 2) and the fourth Damping network (127) have a non-linear characteristic similar to that of the first receiving circuit (20) received nen signals pressed in a predefinable strength and those of the second Receiving circuit (24) received signals are given in a predetermined strength stretched on the transfer channel. 909Ö20 / 1 128